JP2009512479A - Rendering method and apparatus - Google Patents

Abstract

  The rendering method uses volume data 202 that represents the interior of the object to render the surface 102. A position in the volume data 202 having the first parameter is specified. The area on the rendered surface 102 that is placed in the vicinity of the identified location is highlighted, for example by using different images.

Description

  It can be seen that the present invention has particular application to medical imaging, and in particular to rendering anatomical structures such as the colon. It can also be seen that it applies to other imaging applications where it is desirable to highlight regions of interest in the rendered image.

  A virtual endoscope is used as an auxiliary device for visualizing the inside of a lumen such as the human colon or trachea. For example, in colon imaging, it is desirable to identify suspicious masses such as polyps that may indicate early stage cancer. When using data obtained from a CT scan of the colon or other scans, it is typically from one or more three-dimensional areas inside the colon that the user moves through the colon lumen. A rendered view is represented. The clinician uses these rendered images to identify polyps or other suspicious masses.

  Residual waste, fluid or other material remaining in the colon is sometimes difficult to distinguish from colon tissue. For example, in CT imaging, these residual materials have approximately the same value as the radiation attenuation value of the surrounding tissue. As a result, these residual materials sometimes mimic or obscure polyps.

  Various intestinal pretreatment techniques have been implemented to address this issue. In the case of CT imaging, these techniques typically involve the administration of a caliber containing a material that is opaque to radiation, such as barium. The present invention is that the material remaining in the colon is highlighted by the contrast agent.

  One type of intestinal pretreatment is the so-called wet pretreatment, which often leaves a large amount of residual liquid. Another type of intestinal pretreatment is the so-called dry pretreatment, which is dominated by opaque excrement where residual material is often concentrated in the form of balls or clumps near the colon wall.

  In wet pretreatments, tagged liquids and excreta can obscure polyps and other lesions. In dry pretreatment, tagged materials can mimic polyps and other lesions. In particular, the remaining waste appears as a polyp-like mass in the rendered image. The scan contains residual material that obscures a portion of the colon wall, as well as residual material that mimics a polyp or lesion. In either case, these presences can cause confusion and add an extra workload to the clinician. The clinician typically must evaluate and dispose of them.

  Aspects of the present invention address these issues and others.

  According to an aspect of the invention, a method uses volume data indicative of the interior of an object to render a surface, identifying a position in the volume data having a first parameter value, the rendered Identifying a region of interest on the rendered surface as a function of the relative position of the rendered surface and the identified location, and enhancing a human readable image of the rendered surface on the surface Generating with the displayed region of interest.

  According to another aspect of the invention, an apparatus comprises: means for using volume data indicating an interior of an object for rendering a surface; means for identifying a position in the volume data having a first parameter value; Means for identifying a region of interest on the rendered surface as a function of the relative position of the rendered surface and the identified location, and a human readable image of the rendered surface on the surface Generating with the region of interest highlighted in.

  According to another aspect of the invention, a computer-readable storage medium, when implemented by a computer, uses volume data indicative of an internal anatomical portion of a human to render a surface indicative of the interior of the colon. Identifying the region of the rendered surface suspected of containing residual waste and highlighting the identified region on an image of the rendered surface Contains instructions to be executed.

  Still other aspects of the present invention may occur to those skilled in the art upon reading and understanding the accompanying drawings and description.

  The present invention has been described by way of example and like numerals are not intended to limit the form of the accompanying drawings to indicate like elements.

  FIG. 1 represents a rendering of the interior of the colon 102 rendered according to conventional rendering techniques based on volume data obtained from a CT scan. In particular, the colon 102 is rendered as an isosurface with a desired voxel value. Region 104 appears as a suspicious polyp or lesion. However, a more detailed examination of the data set may include residual opaque waste where region 104 mimics a polyp. This opaque excreta is characterized by greater radiation attenuation than the surrounding colon tissue and / or mucosa. When rendered from a viewpoint that is inside the lumen, the partial volume effect near the surface of the opaque excrement occurs in the region 104 being rendered as part of the colon wall. As a result, this region 104 is difficult to distinguish from a polyp.

  FIG. 1b represents a second rendering of the same data set, where the region 104 is suspected of containing residual material and is electronically tagged or highlighted for presentation to the user. As described, the region 104 is indicated by a line 105 such as a contour. In other embodiments, region 104 is displayed in a different color than the rest of colon 102. Of course, other coloring or highlighting techniques may be used, such as using shading, surface textures, arrows or text individually or in various combinations. To simplify the task of viewing and evaluating the rendered image, the tagging causes the user to focus on the suspicious area 104 without substantially obscuring the suspicious area 104 in the rendered image 102. Is generally desirable.

  The rendering process is described in connection with FIG. A volume data set 202 is obtained, such as a data set generated by a CT scanner after appropriate bowel preparation. In an embodiment particularly suitable for identifying residual material that mimics a polyp, an intestinal pretreatment to dry is performed.

  The data set 202 is imaged as an x, y, z array of voxels containing information about one or more physical properties of the object, eg, radiation attenuation of the object. Radiation attenuation is expressed in Haunsfield units (HU), in which air has a value of -1000 HU and water has a value of 0 HU. A larger value indicates a larger radiation attenuation value.

  At 204, voxels suspected of containing residual material are identified. This is accomplished by segmenting the data set 202 according to voxel values to produce a segmented data set or binary volume 206. In an embodiment suitable for imaging the colon, segmentation is performed by thresholding to identify voxels that are expected to contain residual material. In one embodiment, the threshold is set to +200 HU.

  To avoid highlighting noise or areas of clinical interest, segmented areas that are smaller than the desired threshold magnitude are discarded. This for example disposes of a segmented area (approximately 5 mm in diameter) that is smaller than the lower limit of the clinically relevant polyp.

  At 207, the segmented data set 206 is expanded to generate an expanded data set or binary volume 208. In some embodiments, tertiary expansion is performed. In particular, background or non-segmented voxels that touch the segmented data set are added to the expanded data set 208. In the tertiary extension, this process is repeated three times. As will be described in detail below, lower or higher order expansion may be performed.

  At 210, the data set 202 is used to render the desired region of the colon 102 from a viewpoint typically located within the colon lumen, according to an appropriate rendering technique. Such a position will typically have a value for air or a Hounsfield value close to it. In such a technique, explicit segmentation operations are performed on the data set 202 to generate a segmented data set. This segmented data is typically used to approximate a surface represented as a polygonal mesh. An example of such a technique is shown in US Pat. No. 6,083,162, entitled “Method and System for Producing Interactive, Three-Dimensional Renderings of Selected Body Organs Having Hollow Lumens to Enable Simulated Movement Through the Lumen”. In another technique, the position of the isosurface is directly calculated during the rendering process. For a given ray passing through the data set, the position of the voxel through which this ray passes the desired isosurface value is determined. The position and orientation of this isosurface can be obtained by interpolating surrounding voxel values. An example of such a technique is shown in US Pat. No. 6,522,324, the title “Deriving an Iso-Surface in a Multi-Dimensional Data Field”. In one embodiment, the colon 102 is rendered as a surface with a radiation attenuation value of -800 HU.

  As described above, the rendering process may mimic the appearance of the rendered surface 102 with residual opaque material. From that point of view, it can be seen that the voxels in the dataset 202 containing the residue are behind the rendered colon 102, the distance of which is the radiation attenuation of the residual material, the selected threshold and the voxel's Strongly dependent on size. Other relatively attenuated materials, such as bone, are placed further away from the colon 102.

  The dimensions or number of dilations performed at 207 are selected such that voxels representing the residue are expected to intersect the rendered colon 102, while bone and other materials are not expected. In other words, when viewed from that perspective, voxels in the expanded data set 208 resulting from residual material can be expected to be placed in or in front of the rendered colon 102. . Regions where the expanded data set 208 intersects the rendered colon 102 are highlighted, for example by displaying these regions in a different color.

  In implementations where the colon 102 is rendered using ray casting techniques, a first set 212 of video or display attributes (eg, a first color or range of colors) is a voxel of the expanded data set 208. Assigned to. A second set of images 214 (eg, a second color or range of colors) is assigned to the rendered colon 102. As each ray traverses, the colon 102 is placed and displayed using one of the images 212, 214. However, the video 212 showing suspicious voxels takes precedence over the video 214 showing the rendered colon 102. Accordingly, the region where the expanded data set 108 intersects the rendered colon 102 is displayed using the first set 212 of images.

  In other implementations, the desired video is predetermined before rendering. Of course, other implementations are possible.

  The rendered surface 102 is displayed along with the highlighted area 104 on a human readable device such as a monitor or display. This rendering is typically done from each of a plurality of viewpoints and locations as the user moves within the colon lumen.

  As described above, the region 104 suspected of containing residue can be identified using an extended technique. In an alternative technique, the distance between the rendered colon 102 and the segmented data set 106 can be directly calculated either before or simultaneously with the rendering process. A desired image is added to the rendered colon based on the calculated distance.

  While the above discussion focuses on datasets generated by CT scanners, the technology is used with datasets generated by other modalities such as magnetic resonance imaging, ultrasound, SPECT and PET. It is also possible. These techniques can also be applied to imaging of body parts other than the colon. These techniques are not limited to highlighting residual material, but can also be used in situations where the material of interest is suspected of being obscured or imitated by the rendered surface.

  The described techniques can be embodied in computer readable instructions using dedicated hardware or a combination of both. These instructions are stored in one or more computer readable storage media in a remote computer, such as persistent or variable ROM, RAM, variable or persistent CD, DVD, and communications such as the Internet, telephone lines or wireless communications It is carried by the medium to the host system. When implemented by a computer, the instructions cause the processor to perform the techniques described.

  Of course, changes and alternatives will occur to others upon reading and understanding the above description. The present invention is intended to include all such modifications and alternatives as long as they fall within the scope of the appended claims and their equivalents.

A rendered illustration of the interior of the colon. A rendered illustration of the interior of the colon. Data flow diagram of electronic tagging technology.

Claims (20)

Using volume data representing the interior of the object to render the surface;
Identifying a position in the volume data having a first parameter value representing a physical characteristic of the object;
Identifying a region of interest on the rendered surface as a function of the relative position of the rendered surface and the identified position; and a human readable image of the rendered surface Generating with the region of interest highlighted above. The method of claim 1, wherein
The object is a human and the region of interest includes the interior of the colon;
The first parameter value indicates residual material contained in the colon;
The surface is rendered from a first viewpoint, and the method includes identifying a position in the volume data having a first parameter value indicative of the residual material and located behind the rendered surface. Method.   The method of claim 2, wherein the residual material is opaque waste.   4. The method of claim 3, comprising using a first video to render the surface and using a second video to highlight the region of interest.   The method of claim 4, wherein the first video includes a first color and the second video includes a second color.   The method of claim 1, comprising segmenting the volume data as a function of the first parameter value to generate segmented data.   The method of claim 6, comprising the step of expanding the segmented data, wherein the step of identifying a region of interest identifies a location where the rendered surface and the expanded data intersect. A method that includes a step to do.   The method of claim 1, wherein the step of identifying a location is performed prior to the step of using volume data.   The step of using volume data includes rendering the surface from a viewpoint where the parameter has a second value, the surface indicating a position where the parameter has a third value, and the third value. The method of claim 1, wherein is between the first value and the second value.   The method of claim 9, wherein the parameter is radiation attenuation and the first value comprises a value greater than a threshold value. A means of using volume data to indicate the interior of the object to render the surface;
Means for identifying a position in the volume data having a first parameter value representing a physical characteristic of the object;
Means for identifying a region of interest on the rendered surface as a function of the relative position of the rendered surface and the identified position, and a human readable image of the rendered surface, An apparatus comprising means for generating together with the region of interest highlighted above. When implemented by a computer:
Using volume data indicative of an internal anatomical part of a human to render a surface indicative of the interior of the colon;
Performing in the computer a method comprising: identifying a region of the rendered surface suspected of containing residual waste; and highlighting the identified region on an image of the rendered surface A computer-readable storage medium containing instructions to be executed.   13. The surface is rendered from a viewpoint, and the identifying step includes identifying a position in the volume data that has a radiation attenuation greater than a threshold and is located behind the rendered surface. The computer-readable storage medium described in 1.   The step of identifying includes segmenting the volume data as a function of the radiation attenuation to generate segmented data and extending the segmented data to generate expanded data. The computer-readable storage medium according to claim 13, comprising:   The computer readable storage medium of claim 14, wherein the identifying step includes determining an intersection point of the rendered surface and the expanded data.   The method of claim 12, wherein the identifying step includes identifying a location in the volume data suspected of containing residual waste and determining a distance between the identified location and the rendered surface. The computer-readable storage medium described.   The computer-readable storage medium of claim 16, wherein determining the distance includes performing an expansion.   The computer-readable storage medium of claim 12, wherein the highlighting includes using a first image for the rendered surface and a second image for the identified region. .   The computer-readable storage medium of claim 18, wherein the first video and the second video include different colors.   The computer-readable storage medium of claim 19, wherein highlighting includes using a contour line.

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